Though WEB API too requires the object to be sent in JSON form, it differs a little in the way the values for fields that support complex data type are set. The aim of this blog was to take up most of the common data types used and provide a sample code around how the values need to be set of each of these

Lookup, Regarding and Activity parties being special complex field need to be set by providing a reference to the entity type that you intend to set. The field name also includes a reference to the entity as can be seen in the sample code above. This differs from the way it used to be done earlier where entity type used to be provided as a property of the Lookup object instead of in the field name itself.